The presently disclosed device relates to the measurement of eye movement. Regarding eye movement measurement devices, the prior art required precise adjustments for each subject, and complete to partial blocking of the subject's visual range which detrimentally inhibited testing capabilities. Certain devices limited the subject's mobility by requiring the subject to remain perfectly still during measurement. These prior devices were designed to be worn as goggles, helmets, or spectacles which housed the measurement technology.
The main types of eye movement measurement and monitoring systems in common use are: Infrared; Video; Electro-oculography; Limbus trackers; Purkinje reflection trackers, and Scleral Coil trackers. Limbus trackers are usually cheap and easy to use but generally these are only useful for measurements in one axis at a time, that is, they are not gaze monitors. For accurately assessing point of gaze the most common method is the video tracker, where the pupil or iris is imaged using a video camera and a simple image processing module extracts point of gaze, pupil diameter, and in some advanced systems ocular torsion all in real time. The disadvantage of video is that generally the sampling rate is restricted to the video frame rate, making such systems less suitable for looking at parameters such as saccadic latency. Purkinje reflection trackers may also be used as gaze monitors and have a high degree of accuracy and good temporal resolution but are very difficult to set up. Finally, Scleral coil systems, in which a small coil is placed on a contact lens and its position measured within a large frame bounded by other coils, allow measurement of point of gaze and ocular torsion at high spatial and temporal resolutions. However, Scleral coils are invasive, such that a hard annular contact lens must be attached directly to the eye, which typically has a maximum wearing time of 30 minutes.
The present invention overcomes the shortcomings of the prior art by requiring minimal adjustment for accurate measurement of horizontal and vertical eye movement utilizing direct infrared illuminators and sensors, only minimally obstructing the lower portion of the user's visual range, being made of low cost and readily available material, and by being comprised of a comfortable and efficient design of an adjustable nose bridge with the measuring and calculation means attached thereto. The presently disclosed device requires only a minimal aperture or frame, and, does not require any additional optics such as, lenses, mirrors, or prisms as did the prior art.